Spark plug



1 Aug. 13, 1935. V A. E. HORNBACK SPARK PLUG Filed Aug. 18, 1954 JizJerzzor:

1 072 Zflornbacfi, m i M Patented Aug. 13, 1935 PATENT OFFICE SPARK PLUG Arch E. Homback, Chicago, Ill., assignor of oneeighth to Chas. S. Deneen, three-sixteenths to Walter G. Davis, one-eighth to Gilbert Hardy, one-sixteenth to Emma Schumacher, and onefourth to Albert Wilkinson, all of Chicago, Ill.

Application August 18, 1934, Serial No. 740,472 9 Claims. (01.123-169) This invention relates to spark plugs for internal combustion engines.

One of the objects of the invention is to provide a spark plug in which the porcelain parts are protected from the high temperatures existing in the combustion chamber of the cylinder. This object is partially accomplished by means of the construction of the center and intermediate electrodes whereby the plug end is bailled' and the porcelain cores are almost completely enclosed and protected by heat resisting metal. The electrodes do not project beyond the end of the plug into the combustion chamber, and the end of the plug, as 'a whole, does not project to any appreciable extent beyond the water' jacketed wall into which it is screwed. This arrangement also assists in preventing destruction of the cores.

Another advantage of the baille construction to be described is the fact that in the event any part of the porcelain core should break, no particles of suflicient size to cause damage can pass into the cylinder.

Another advantage of my invention lies in the construction whereby a scavenging effect is produced on the sparkareas or surfaces, thus keeping the plug eihcient for spark output. The ignition of gas in the small gas chambers within the plug, having restricted communication with the combustion chamber of-the cylinder, occurs more quickly than complete combustion does in the cylinder and thus there is produced a blastof gas from the plug through the narrow spaces between the ring electrode and the shell with a plug embodying my invention' Fig. 2 is a bottom view of the same. Fig. 3 is a bottom view of a modified form of construction.

In that embodiment of my invention shown in Figs. 1 and 2, III indicates a steel shell which is threaded at H to adapt the same to. be screwed into the water jacketed cylinder head i2 of an internal combustion engine With the end of the plug substantially in the plane of the cylinder head. Within the shell l thereis positioned aheat-resisting porcelain core l3 carrying a central electrode I which is provided at the bottom with an imperforate dished disc i5, held by the end l4, and is provided with a shoulder I 6 adapted to abut against a shoulder I! in a central bore iii in the core l3, said bore being enlarged at the bottom as indicated at l9. Said electrode -45 is adapted to be held in place by means of a nut 20 threaded onto the upper end of the electrode. A nut 2i is threaded onto the upper end of the electrode it to form a binding post in the usual manner. A clamp nut 22 fits over the upper part of the core l3 and is screwed into the top of the shell It as indicated at 23, a copper gasket 24 beingpositioned between the lower end of said nut and a shoulder 25 on the core l3. Another gasket 26, preferably made of nichrome, is positioned between a shoulder 21 on the lower part of the core l3 anda shoulder 28 formed in the shell I0. I

On the lower end ofthe electrode I4 is a smaller porcelain core 29 which is non-reciprocably held thereon between the disc I of the electrode l4 engaging the lower end of the core 29 and the lower end of the core i3. 'The core 29 carries an intermediate electrode 30 in the form of a cupped ring which practically encloses the core. The outer end. of the ring .3015 flanged outwardly. the periphery thereof being spaced a suitable distance from the inner wall of the shell Iii.

Due to the intense heat generated when a spark plug ,of this character is used, I find it desirable to use a special metal for the intermediate electrode 30, such as the alloy known as nichrome or Marmet, which is non-expanding and has excellent heat-resisting qualities. The central electrode i5 may also be made of nichrome or other heat resisting alloy. Marmet" is the trade name of a heat resisting alloy made by Wilbur B. Driver Company, Newark, New Jersey, by a secret process. 7

As shown in Figs. 1 and 2 the electrode disc ii, the intermediate electrode 30 and the shell iii are concentric, and, therefore, the annular space 3| between the disc l5 and ring 30 is of uniform width, and the space 32 between the ring and shell I0 is likewise of uniform width.

In the modification shown in Fig. 3, the intermediate electrode 30' is shown as slightly eccentric to the disc ii and shell 10, so that the space 32' between the electrode 30' and shell I0 is not uniform, and the space between said electrode 30' and the disc I5 is not uniform. The result of this arrangement is that the spark will jump tween the disc i and electrode 30', and between the electrode 30' and the shell III. This arrange- 'ment is not essential to the successful operation of my spark plug, but is of -value in providing two spaced apart sparks.

In some prior art structures, intermediate electrodes have been arranged for automatic reciprocatory movement on the central electrode, for the alleged purpose of preventing carbon deposits, but this construction is open to the objection that the movable electrode does not always resume its intended position relatively to the fixed electrode and the sparking relationship of the electrodes is thus impaired. Another objection is that such plugs cannot be used in radial eng'ines, wherein some of the plugs are necessarily in inverted or non-vertical positions. Therefore, I avoid these objections by mounting my electrode 30 non-reciprocatorily but non-rigidly on the electrode stem ll; The electrodes are kept free from carbon by the scavenging effect of the combustion which occurs in the baflled gas chamber of the plug and by the fact that my electrodes l5 and 30 are preferably made of nichrome or other suitable heat-resisting metals.

(.lhanges may be made in details of construction without departing from the scope of my invention and I do not intend to be limited to the exact form shown and described, except as set forth in the appended claims.

- I claim:

1. A spark plug comprising a shell which functions as an electrode, an insulating core in the shell, a central electrode mounted in the core, a second insulatingcore mounted on the central electrode, an intermediate electrode surrounding said last mentioned core and having its lower peripheral edge substantially in the same plane with the lower end of the central electrode and the lower end of the shell.

- 2. A spark plug comprising a shell which functions as an electrode, an insulating core in the shell, a central electrode mounted in the core,

- a second insulating core mounted on the central electrode, an intermediate electrode surrounding said last mentioned core and having its lower peripheral edge substantially in the same plane with the lower end of the central electrode and the lower end of the shell, the intermediate electrode being concentric with the central electrode and shell. j

3. A spark plug comprising a shell which functions as an electrode, an insulating core in the shell, a central electrode mounted in the cor.e,

tions as an electrode, an insulating core in the I shell, 9. central electrode mounted in the core, a second insulating core non-reciprocably but non-rigidly mounted on the central electrode, anintermediate electrode surrounding said last the shortest gaps located at opposite points, be-

mentioned core and having its lower peripheral edge substantially in the same plane with the lower end of the central electrode and the lower and provided with a relatively large disc at one end, a second insulating core mounted on the central electrode, and an intermediate electrode surrounding said last mentioned core, said intermediate electrode having a tubular body slightly flaring at its lower end.

6. A spark plug comprising a shell which functions as an electrode, an insulating core in the shell, a central electrode mounted in the core and provided with a relatively large disc at one end, a second insulating core mounted on the central electrode, and an intermediate electrode surrounding said last mentioned core, said intermediate electrode and insulating cores forming with the shell an annular, baflied gas chamber within the lower portion of the shell, said chamber being of greater cross sectional area intermediate its ends than at its exit end, and gradually diminishing in cross sectional area towards said exit end.

7. A spark plug comprising a shell which functions as an electrode, an insulating core in the shell, a central electrode mounted in the core and provided with a relatively large disc at one end, a second insulating core mounted on the central electrode, and an intermediate electrode surrounding said last mentioned core, said intermediate electrode and insulating cores forming with the shell an annular, bailied gas chamber within the lower portion oi. the shell, said chamber being of greatest cross sectional area adjacent the proximate portions of the insulating cores and gradually diminishing in cross sectional area near its exit end.

8. A spark plug comprising a shell which func-' tions as an electrode, an insulating core in the shell, a central electrode mounted in the core, a second insulating core 'non-reciprocably but non-rigidly mounted on the central electrode, and an intermediate electrode surrounding said last mentioned core, said second insulating core being of minimum diameter at the end abutting the first mentioned insulating core.

9. A spark plug comprising a shell which functions as an electrode, an insulating core in the shell, a central electrode mounted in the core and provided with a relatively large disc at one end, a second insulating core mounted on the central electrode, and an intermediate electrode surrounding said last mentionedcore, said intermediate electrode and insulating cores forming with the shell an annular, baflied gas chamber within the lower portion of the shell, said chamber being oi greater cross sectional areaintermediate its ends than at its exit end and gradually diminishing in cross sectional area towards said exit end, the lower peripheral edge of the intermediate electrode being in substantially the same plane as the lower end of the central electrode and the lower end of the shell.

ARCH E. HORNBACK. 

